The most common and most likely answer to this crossword clue is the 4 plus 7 letter word STAR CROSSED
I've seen this crossword clue in Independent
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More clues leading to the result STAR CROSSED
Buddy explains!

The straight part
We know that "as lovers, like Romeo and Juliet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case as lovers, like romeo and juliet = star crossed.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does STAR CROSSED mean?
STAR CROSSED adjective- Ill-fated by destiny, the fate of the person being “written in the stars”.